Lecture Notes and Memoranda Prepared at Steep Rock Lake, Ontario

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Lecture Notes and Memoranda Prepared at Steep Rock Lake, Ontario

http://irc.nrc-cnrc.gc.ca

L e c t u r e N o t e s a n d M e m o r a n d a P r e p a r e d a t

S t e e p R o c k L a k e , O n t a r i o

D B R - R 1 3

S u t h e r l a n d , H .

J u l y 1 9 4 8

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AP: ALY L - 3

He:

S'IWPPIAIG OF

CLAY

E'ROPi TIE3 S OUTH UJD OF TILE flBfv CXERIDY

The

fol-lo:,- notes have been w r i t t e n after study of a plan psesetlted

by

Ki,

. k! S m e l xlegm-ding the clay strLpping

from

the South end of t h e 11i3'1 Orebody, I&. S a m ~ - % e l propses to reduce t h e vzbrvsd clajr to a level of" appro- x h a % e l y

lJ.45

feet bn two operat,5.0ans the clay ec; removed flowing to F a l l 8 b y , Tie s b p e s 50 t h e p i t are t h e n to be fomled by s l ~ i c i n g and puniptng t h e inaterial to Falls Bay,

PbdificatLons to this plan w e sug,.;?s-ted, n o d i f i c n t i o n s which

call

for Xess removal. of r&%erie?l, LS mi'iing R e i ~ t ~ t u of banks for lmrticulan. slopes

of 5mks are a l s o saggested,

'The Analysis of .4; he

Stab~l~~~o,ff'~.l~l~u,.

If an

sartil r~e.33 consists of a granular m a t o r i d such as sand or

gp.sve3- e f ~ d it is A e s i ~ e d t,o c u t a slope in I t , then the mass ~ 1 5 1 d 3 . m y s 5e

1,

sb.l~Le despite t h z $eight, of t h e ccat slope, provided ttae slope is lese than

the angle of repuse of t he rmt erlal, t h e a n g l e of repose beiw e qvd. to the angle of i n t e r r n . ~ fricti.on of t h e ~nater:L<S f n its looaest s t a t e , Such a cond-

i t i o n i.s net true

for

a cohesive material. dith such soil, 3 cut

40

feet h3.gh

at a s!.op of 1 in

3

nay be stable while a sSnilar slope in the s m s i n a t w i d 80 feet, high may rail, %'he soil at, Steep !?oS~k Lake comes into t h e cohesive

categozy, The p-loblem of atabilizi~g the s 1 ~ g e s therefore docs not become one of f ' i d r l g one given i n c l j n a t 5 o n and s t i c H n g to it throughout but is one cP

ad&stiuig slopes in the I l g h t of the depth to which t h e y are ark, and imp5sing

L

l 9 r i l . t ~ ~ i u e l z on t,he dcight to which a giver, slope should be cut,

Re

..

StripgiPg

of

C l a y from

the

Soutih EnQ

of the "Bn

Ora,&. [Pago 2

f iret i e r

failure

by

e l i d i n g

of the

8011

on

a

oirwlar aro, Th4 eewnd

by

the struotura

of

t h e 8011

bra-

do- and a failure by 8 ~ m a d r x

rlw

resulting,

Ea&

of

them

types of

failure l o deaoribsb in

d e t a i l I n t h e foUorring

nates

and an attempt 10 made

t o present

analytiaal

methoda

for

dealing with

eaah

type,, Tbm seoond

t y w of f a i l u r e ,

by flow aud spread,

preeants

a

d i f f i c u l t

probla of

analyaia

dm

t o

tha unknown quantity

oiz, t h e water

presew'e in tbe

porw of tho

m i l .

m e

form

of f m i l r ~ u & that whloh ha8 oawed most

t r o u b b

a t

Steep Rook,

and a l l

poesiblm sarie-de

m u d t

be taken t o

prevent a

recurrenoe,

(a)

Failure

b y

Sliding alone a

C i t o u l a r Axo

The

f i r s t a m l y ~ e e

of t h e

oauaes

of f a i l u r e of e a r t h

elopes

-re

undertaken aa

a

result of

a

nunber

of

dieaetroua f a i l u r e e in

r a i l road

ambankmonte

in Sweden,

fnvsetigatlone of the

surfaoa along tihioh f a i l u r e

took

plaos showed

t h a t

it

approximated t o

a o l r o l i l a r a r o , and as a

r e s u l t

ths CircUaz Aro

Method of Analyeirr

was

dsoaloped,

Reisrenoe t o

F i g o 1 ehowa

suoh

a

fona

o r fail-, !b

s u r f a m

A B C

of t a i l w e

i e

presumed

t o be

o l r u u -

lar and failure

takes place by

tbs

earth

mmo A B C D moving

about

tbe

o e n l e

of r o t a t i a n

0 , T3m

dilrturblng moment

oawing f a i l u r e

is

t h s r e f o r e t h e

weight

of

t h e

e a r t h

wcs

times

the

diatanoe betwen

param1 lines d r b

through

ifs

oentroid

and

point

0 ,

i , e , tho

disturbing moment o IR i

Bailure

is

r s s i e t e d by

the ahear

strength

of

t h e

8011

t h a t

is

mobilized

along the a r o A

B

C ernrdl the

r e s i s t i n g moment

is -18

t o t a l

ehear strength times the

radiue

of

the airotilar era

along

whioh f a i l u r e

takes plam, The

moil

w

ham

varying

ahear

strength

along arc A

B

C aa8

t h i a

ehould be

taken acoount of

b the

analps&sp

R e : S t r i p p i n g

.-

of

C l e w

from

the

South

End of

the

"Be

Orebody

( m e

5)

HMse 8 _Ths shear Utrbngth

of tho e o l l ,

aeeumlng it to be homogeneoue

A l Len&thof the a r o A B 0

R

r

Badiue of fallure cirale

Ths

factor

o f Safety s a i n s t failure W 'Phs Reeieting mament

-

The

Disturbing moment

While a faotor of adety

of

3

or

4

ie

ueual

In

S t n o t w a l l Enginasring

Aeeign, atab@e seater than 1,,8

are

U U I B ~ ~ ~

i n t h

daeign of earth slopee,

e a ~ t h dtuw and elmiltar struo.9;uresc, Larth dama

mat

have been designed recently

in the United State8 bavle had

factor8

of safety

of

1,8

t o

%,,So

In

such

f 3 t r u c t ~ e S rigid 00ntr0l of the ccxnpaa%ion

of

the placed soil i s e x ~ e r c i s s d

during construction,

Wbon ohaeking %ha a t a b i l i t y o f existing s w t h alopea, the fw f a a t - -

or8 which m w t be de'termimd are the rradfue of the OPrcle of fallwe aria the

The radius of the f a i l u r e c i r a l e

must

be datemined by .trial and

error

so a8

to

give the smallest value of factor of wafe%yo

Re::

Strippin& of C l a y from the South Tad of the PPBFO Qrebi)Q -= (paG: B i

A @mdleh S q i n e e r , Fallsmiw, who investigated the e#ly slope failures which occurred

i n

h i s country, h a published

a

table which assists in

a

more

rapid determination of t h e centre, of the oirole of failure where ths soil

oonosmed is homogemoua and uniform,

D,, I,

Taylor haa publi~lhed i n gtaghioaf form a mathod whereby the

s t a b i l i t y o f

an

eerth slope of homogeneous

material

aan quiokly be determined,

Professor

Taylor doee not claim t h a t his method, wnd .the aeeumptions made, GIWB

an

exact anch completely accurate metbod of analysisn Eumver, t h e very

nature of s o i l , and tho v a s i a t i o w In it, l a such

es

t o make any t h e o r e t l c a ~

nnalysia

subjeat

f,o error when applied t o

a

p r a c t i c a l problem, The i n t e l l i g e n t

use of the Taylor method, i n conJurction with thorough Investigations of a site

ahowing an easentidEy homogt+moua e o l l , sbouLd give i n f o m a t i a n t o the oil

engineer whicrh c m aerva aa Q

very

useful guide fm design- The Ta;gior cwmms have been ussd in the s l o p

analysie

carried out in t h i s ~ 8 ~ r ~ r a A d m , thia

amXysls b s b g oo~cernsdi only sf oaurse with stability against f a i l w e along a

19ee shear etrength of a ~ o h l can. be determined i n a number of ways,

the two moat important and frequently w e d being the direct action s h e a ~ box and

the t r i - a x i a l oompxessioe apparatus,, Tbs shear box and the nature

of t h e t e e t s performed w i t h it, have been 8iscwsed in a previous mnemoragdum t o

Mrf, Kc, Lo YcRorla, With the, tri-=ax%d camgreeeian a p p a r a t u s the epecWn f8 plaued

Inside er l u u i t e sp-linder, a oylinder i n which an a i r o r water pressure can b e

buile

up to any dasired

value,

When t h i s l a t e r a l preemare l o

built

up,

an

axial

pressure i s a p p l i e d t o the oylindrical specimen by mean8 of a piston and the

epcinnen l e loadef

t o

failure, The a x i a l pressure, o d l e d the

m j o r

p r i a c i p d

etrgss corresponding t o the lateral pressure, called the minor p r i n ~ i p a l s t r e o @ ~

RE; S m i n g ; ? G l e x o m t h e South XnP c f the R B m [gaga 5)

..-

-1--* ---=-

-

'Ilta mador and rei.nor prlnolpal streasea a r e plo-bted and a relationehip c w

%hen be obtain6.l for the ehcstw strength of She soil,

C 2

"

T

Quick

Teat

1

Uncsn4in.d c a p * * ~ i * n ?el+

f i

s

or a x i a l 6treBr,:m :, a mtp&k t e a t IQ res~lilte, 3Ef full consolidat ion i s allowed under "te SatarsP s t ~ e s e alone, a w ~ ~ o n ~ o l i d a ~ e d w k

_-"-

teat* resulea,

If

fa1 ~avlsolidaticl~ I s allowlad under 'both lateral a d mink stresses t h e result- %.% t o a t oalk.@d a vT_BI~~ t ~ 8 $ * ~ a i ~ i k % c a n c e 0% the Oeat results has

be@e ~sqXained l u a prevj,~us mma on the sltncea~ box,

B s t l the shear box aud t h e trl-axial compresslorn apparatus are

expeaaive pdecr-IS of' appwatus a 8 are not availcnble at Steep Bock, A mod-

i f i e d f c m of %he tri-axial oompreaeion a.pparatu8 aan easily be constructed

so t b . t ~ t wqulok t e a t s R can be

rmn,.

'Hlaie I s known tat3 the unconfined compression

Re: Stripping of Clay from tho

-

South End o_f tho 'OBn Orebode _{[page 6 \} pressure and a l l y an a x i d . pressure is applied to give f a l l w e , _&om %be

pPols of the d4,fferes-t t y g s s of terrts shown

in

F P w e 2, _{it can b e seen}

that the ehear strength ~qw3.8 one half the wmpreEision streae In the

nquiokw tesP, *i,e, the p l o t of shear strength is a line parallel to the

base and with $

=

o.

Obasr~~ations QT failureo of earth slope6 and dama i n Great Britain

agd the United States have ahom that vfhere euoh f ~ i l ~ a r 8 8 C ) C C U X ' ~ B ~ iu clay

material that +;he ahem strength along the w c 0% faailwe was equal t o one3

half the unoorl.'ixned compression Gost in&, equal to the shoas strength value obtained from the m q ~ i ~ k F q t e a t o

An unconfined comprasslon device has been constructed i n the machine

8' -\;3" at %sep IZock, and the valurs of sshe4ar etrength s ~ u a l to oxas half t b

~inconfbned c~n;~,resslor, strength have buen used Im stabilltiy coqutrationa,

T e a t Resu1ts

'Op to the t irce OF writing ( late Jim@ 1948) , only relatii-woPy f e w

~ ~ e s n f i n s d com,~lcession testa haas been mads, Thewe "bvaata, aboaa'c 30 in n~mbar,, give r,i averegE value of shear stronglh of about 4 Bb. per aq,

In,

"- 576 Ib, per jq, %t, and t h i s value haa been w e d throughout An the cab= eulations

-

R e ~ e a t e d checks should be made sf t h i s v d w RS the $as% fs a

simple one to ~ e r f o m , a! some modif Icatlon may be necessary t o this valw,

A fac;t,ar of safcrty of 1,25 hiis bean d o p e d tbougho~xb Pn t b calculations,

R a m ?iP C b q from @he Sowkh s f the

*BQ

O ~ e b ~ d m

--

" ",--.- -----.-PP--P-,

b )

-

FaiZ;urarr b ; - a r s a d m d Flow o f the V a s ~ o d Clay

The f am sf f a i l u x e dmoribad wder l h ~ a b i n g [a] v i z , %he fail- ure along a ciruzalar a r c , i t ! %ho type of failure moat o o m n .b ham-

gBmeeoW alays au8 wbeslvt3 nnd%ter;bals, With slaterids eueh a8 v a ~ v e d o l w y ~

where, t b r e exLi4.t layere of gilt, O P aimiPw relatively comoe uateriali

a

which i a water ;learing, t h w e occ~slra different ty-p of feilurs, Fenst=*

r n t i o z of *m.ter ??rum m ad;laasut higher waWr tablo into these bayere allom

s water p r s s s w : ~ to bs buXi.2 up in t h e pore8 of t h e material, %be atability of the soiL mast f a degcalcdennt

on

the hear ~trsngth of Qe soilc ThfB i3baa"

etreiagth i s a. %qaxot20n 09 \-,ha effeuti~a pr8eeure i , , e ; , . tha greaeuxe transmitted

from grain t o qgl sin in thcl 8013. mass, A pose pressrere acts oppos It@ t c t U e i

a f f e c t i ~ e prcsasiyss a d SO ~edueea i t l thm r~duaing %he B B I B ~ ~trsngth of

the soil and thu a t a b i l i % y o f *he sPoger A. charactarlw$fo of t h l e t o m of

fad;Ews i s the cuddamass

wI%h

which il; takas pPaoe m d BP" tihe material

In

~Hhioh it Q O C ? ~ ~ ha81 Q ~ e u t i i t i v ~ a,bructupe i s ooxldftion wriacllly asmcla%hsd

w i t h high aa%~.?k:i mZeP c(dnto~%a;), the8 bl f101 o i ' B ~ B C O U ~ ~l~aPGerlaB r b ~ d t ~ ~ The iaoe"tasvsre af tha elope faiilwfes which have occWrw3 at Stesp Rook havsl

o o m U t o t h i s c atega.ry, w d %ava beon aasoalated w i t h periods o% hi& rain- f a l l ox w i t h pe~3Gratioa sf surface chainage i n t o the ooiX mass, Both these czonditlorm b u i l c up pQrs water prsssww in the water baaking

Awers,

Figo 3

il1uat::atae %he Porn sf failwe,

- - .Im u -

.-

.,.-,,,,,--,-

...---

Y . - - - * - -

--

L

--.me--

--- +

---

I s t \ t a t sand l a y e r s

Re*

--

SCrippiug of -.-

...

, . " l ~ irom the SouthEnd o f

tW9

*Bn Orebo%x (page 8 ) me quffstion has Been raiaed a t tXrnea as t o the e f f e c t af the

a

natural. d i p of t h e verved clay, The direction of the dig cannot p f e c t the machgnica of a s t a b i l i t y analyeis as neither the t o t a l mas (constituting the disturbing e1a~en-t In .l;b s l i d i n g cirole failure) nor the pare water pressure

(the disturbing element i n the flow or spread f a i l w e ) i s influenced,

However,

the nxteat of $he o l i d e where flow or epread oceurs i s effected by the direction 02 the va.'ves ae shown i n Figure 4 ,

Idaterial o w &

flmsamy

so

easUy, end , ~ s e S s t a n ~ e toe

can

be bui18 q ~ ,

Dip of vcirves w i : , h g L ~ ~ Dip of a m s against

aope

Figrule 4

6 )

F f m e 4 siil

h e 4 _{( 1} with the vwvea l y i n g with %ha s1.0pe1, the materieal

once f a i l e d flow8 dom the slope and lends %s prsgressivs failwe by cutting

baak of tbs slope If a p t.t of open exoavari;lon 1.I.a~ some d i s t a e o e down tiha

elope .then the qieccrw mataria1 o m f lorn i n t o t h e pit,'. I f as i n

B

i i ) above the slope of the ~ a r v e s is opposite to the earth

m a s s

slope, then the spread material t,anda t c f l o ~ "upfq the vervels and builds up a too which caxl o i f e r

some resistanas t a further flow

ma

progressive bretakiw back of t;hs material

in thn slogs.

no

r e l l s b l e spinion canbe f a m d conoernlng the iaator of safety

a f tho slope with resj?uot t o flow and spreading unless the pore water pressure i 8 knowno

R e .: 3 t a m @ h y f r o m t b South End of" the mIPw Orebody (gage 9

1

Thle psessure can only bes determined i n the field by pressure gauge obser-

vw'i;Sonar, hrkodla sbsemat ion of the gauge8 oould give v~arniDg of a sblde,

If the obaer'satione

over

a period indloated a how fautor of safety, drainage co~fidl be i n s t e l l e d t o keep the pore water pressure down t o s ~ f e limita,

h t h these greoautione are oxpensive ond time consuming, Unfort-

unately t h i e type of failuse appear8 t o be that whiah oocurred most fregtrgntly at Steep Rook,

Dr,

T e r z e i , thlrir in%ea'nationaP authority on so61 m~chanios, b s

iavoatigatgd the problem and p o g o ~ e d a peeauS109lasy n~eaawe to guard agalrmt fadlurs. Aa menBioned e s ~ ~ l l o r i n thier mennosadm: there i s a orlt-

iatth height t o tvhfoh a &Pmn shop~1, om be o u t in a eah@alv@ material, 3Cr,

Tern@% $NS

8bm

%PJbe~r@ticd,P~ Chat if the I I E L X I ~ ~ I ~ b i g h t of slope Pn a

V ~ V O ~ ! o l a y i a keg3 dovm to Ithe m a x i n u m height to vtbiclh a v e ~ t f o a l . cuk ccaxl be mde i n tho matexaial., then a ~afegurcR o m be grovidsd tigabst failure

bg spread and flow, Sueh a l h i t a t f o n , applied in m n j u a t ~ t i o n wPth a analysie for the oFrau;Zar two type of failme s@ou%d give proteo'clon slgabrst

Pallure,

If

f l o w of ground vatar towards the olay can b e readily divereed t h i s should be done

ae

auch water can penetrate the water bear- layere sf sand or s;b:l.% and b u i l d up a prosaws

in

the pores,

I&

a Icscatittn i n the, Qnited States whiolh as v a v e a clay depoeits,

f l o w failures ilave beern observed at i n t e m ~ l a of' about 20 years, oorresg-

onding t o periods of maximuin rainfall,, The frequency of such failures,

of c o w e e , d e p n d e oa ooxlditiona 02' e x i s t l q water %able levels and the factor of eafa%p @xji.eting .,-ezorc increased pore arater prasswo, and the frequsnoy will vary f r o m glaoae t o plaoe,

Apply3.q

Dr,

Torzaghi08 method, the critical height to which a

vertical out can b e made

In

the vamred aPay a% Stsop Rook is approxlnmtely

22 feet, This valve i s based on the relatively mall nmber of unconfined oomprsssiou t ~ ~ t 8 t h a t have been performed, and

mw

bs s u b j e o t to

revision

as further teats esa perfomad, Born t h i a data,

I

auggceat that the f i n a l

bench intervd.8 b e 20 faet apart verticallye !This should give praterctioo.

a&ainst the psriodio building lap of

pore

water pressuse, Exambatilon of Sectionrs 1 .to 9 shows that in ths more recent +*i;rl=pgilag operatiom the

reoomnda%ion,

The method of calculation al the

maximum

vertical cub i n a clay bank i s elhorn at %he end of .&hese na4'ceso :.nd a copy of Profssso~

Taylor's

Re:

S t r ~ a

o f Clay f r m t h e Soul;h End of t h e "Bn Orebody (Page 11)

COX CLTIS ION

After an examination of M r . Sesrmelgs proposed scheme,' I should like t o make t h e following comenta:

1 am of t h e opinion t h a t t h e clay need not be removed t o such an

extent as sugge,3ted, i.eo t o a l e v e l varying from 114705 a t Section 10 t o ll4.0 a t Section 15. S t a b i l i t y calculations on Section 10 Lo 15 show t h a t benches can be formed a t higher l e v e l s while s t i l l r e t a i n i n g t h e s t a b i l i t y of t h e slopes, Observations of the conditions existing a t Sections

1

t o

9

show %ha% my propoaed amendments do not incur any mre severe conditions than exist i n these sectisncs. Sections 10 t o 15 do not l i e on t h e l i n e of ,geates't slope of t h e clay. Therefore a t a b i l f t y calculations on these sect;iana can bo misleading, and new sections should be drawn on t h e l i n e of

s e a t e s t slope so t h a t a plan of t h e p r o p s e d ber~ches can be properly dram, Hawaver, it i s d i f f i c u l t t o draw a plan view o f the benches p l o t t i n g from sections, aa the sand and gravel l e v e l a vary t o a g r e a t mLsrlt, P l o t t i n g a

plan from the sections givea an extremely e r r a t i c arre~gement of benches due .to the variaticns.

I

have drawn up a sketch plan, which is attached t o this memorandum, i n which t h e trend of bench location is shown, T1ds plan, w%th the approximate location o f t h e bonchea shown thereon, w i l l serve as a guide t o t h e s e t t i n g out of t h e benches, It i s r e a l i s e d t h a t l o c a l conditions and exigencies make i t d i f f i c u l t t o follow a set plan, and t h e sketch plan sub- mltted i s intended be a general guide to the scheme of t h e slopes r a t h e r 'than a r i g i d specification,

Demands f o r production of ore mag a l t e r t h e planning and c a l l f o r

an acceleration of the s t r i p p i n g programe, The following a r e general rec-

ommendationa t h a t should be followed in order t o a f f o r d s a f e t y against c i r c u l a r a r c f a i l u r e s . Theae values a r e based on t h e assumption t h a t the

Reg

S D l r j a $ ~ a f Clay from the

South

End

of the t'Blt Orebody (Page

₁₂₎

t h e and and

gravel l e v e l l i e 8 throughout

a t

approxiaately t h e same l e v e l as

the t o e

of

t h e s l o p . Where the sand and gravel surface p a r u e l a the varved

clay surface, these values are

too

severe and can be

modified,

In

such a

case

individual

slopes

should

be checked as shown i n Figure

5,

. . -

Check e t a b i l l t y from

ic

t o G

Check s t a b i l i t y from

P

t k

A

With slopes w i t 2 20 feet risea between benches,and w i t h berms 50 f e e t wide, s lbmi'ting t o t a l rise of

54

feet

above

the toe is recommended, Greater risecs a r e permissible by widening the berms and 80 f l a t t e n i q t h e o v e r a l l slope,

_The

following t a b l e

gives

t h e r e l a t i o n s h i p between rise and o v e r a l l s l o p ,

Difference

in elevation

between t o e of slops and

c r e s t o f slope?

Horizontal distance

between toe of alope

and c.rest of slope Feet

Equivalent o v e r a l l

slops measured Prom

crest t o t o e of slope

"..

By the use of these figures as a general guide, slopes can be

laid out

on

eections

on t h e l i n e s of %he greateat slope of t h e clay, Protection against c i r c u l a r a r c

Re: Strip- *--- of Clay from the South

-

End of t h e $PBH Orebody (Page

33)

failures can thus be given. By limiting diTerance

in

level between benches to 20 feet, an attempt can be made to stabilise t h e slope against failure by

f l o w and spread. Using a 20 feet rise bekween benches at a alope of 1 i n

3

? and knowing the total rise,the o v e r a l l equivalent slope can be found from the

abovtl. table and t h e necessary widtho of benches determined.

Theee --.-I"--- values hare been based on

a

r e l a t i v e l y

8mll

rider o f t e s t a

c o n s i d e r i n ~ t h e extent of the area involved, Check t e s t s f o r the uglconf ined

com~easion

str211gbl-1 of t h e soil should be carried Q L I ~ at every opportxmitg,

-

--.--

Tho lrLTormation obtained from t h e foregoing analysis is intended as

a guide and m s k be combined w i t h tno observaLions and experience of the

operators on t h e job, _{~ r r , should} not be taken as a r i g i d specification bub

should be used w i t h good Jud~pcnP;, a3 f l e x i b - i l i t y of thought must be retained a t all t b e s ,

o f Clav -,-- from the S ~ u t h

--

]End of the

--

i s B 3 &

(Page 1 1 4 ) Spscimen Calculatj.ons -..: used

in

Slope Analysis

1, ?!o f i n d 'the height to which a can be safeXy cut, t o observe the following condjtiona :

Average valueof shear s t r e n g t h o f clay

h

S

.

4

ib./in2 576 i b / f i 2 0 ! 5 ~ 3 d u e d

3

by "btkylar)

Density of Clay ;

k

-

= 105 lb/ft

.

Bank r i ~ a a at 1. vertizLS. to 3 horieantd for B vertical distmce of 20 feet

has a 50 f e e t berm, rises apain a t 1 in

3

for 20 f e a t e t c . T h i s gives

an

average o v e r a l l slope value o f approxhmtoly

a*,

FacPIor of safety against c i r c u l a r arc failure e 1-25

Ratlo of distance from slope crest t o hard underlying surface to vertical

height of slope

=

B

1. From Taylor @ s r:umes :

0

Stability Number f o r

Dm

1

andd z

13

and

P)

=

o i a 0,81

* C ~ 0 0 8 1 o o o H o C

O D

-

-

-

576

34

Feet.

F ~ H

F.

L

0081 lo25xl05x0. 81

R s s S t r i p , C l a y fromthe Soukh a d of the 'qBLg Ore%,& (page 15)

2, To find the height to which a bank can be cut v e r t i c a l l y

in

a c l a y h a w t h e same properties a s in example 1,

Critical h e i r l ~ t to which a cZAy can be cut vertically

._

3.85

-

S Where S

=

shear strength of s o i l l b / n 2

r

1

density of s o i l 1b/f't3

0 Q

H

z =13.85 x

-

1,

=

approximately 22 f e e t

105

A table is attachedbdow showing. the variation i n t h i s c r i t i c a l height to which a vertical c u t can be i ~ ~ d a as the s h e a r strength and density varisa,

- -- ₄

V

zkx-~~\v

8 47;; ~~,@~&T&JA"F a p l y T a e f

.*-A &@s:~~+&~&2a&k:2:A~~%z:5s

These tesks (L)

me

&uick T ~ s t (11) The Coaseil5dskad Quick TosP, ( U l ) 'Phs

Slm T e s t ,

A

description

of

each c f thsss te@%s

fo3lows,

1.

j, ;;;S -j--i.,& e'.?v"'..<.:]l.~ - = j,, ~r.,~;->-.- I: I

c ."

L,:,?,~.2sy a d k , , L x p *.:! %.;\dtx.-"~. 2~ _.". +, L;>y2z;,;L<2;:~ g.c>d ,..,,, +;2te.,-2 , ,,,,& L . A t + - , s A , ;+:$re;!.s< 8~,ti3&6$;@$ k.3 &

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